The project is designed to evaluate the impact of pregnancy on the health of HIV-infected women, the mechanisms and timing of vertical HIV transmission, rates of maternal-infant transmission (overall and among different sub-populations of at-risk pregnant women), as well as understanding co-factors related to HIV transmission. The WITS program is now into its third funding cycle and extremely important data have been published in peer-reviewed literature and will be published. An example is the HIV viral load data appearing in the May 1997 issue of THE NEW ENGLAND JOURNAL OF MEDICINE. WITS will continue to accrue patients for the next 1.5 years. An RFP is under development for NIH funding for WITS4 initiatives. Which will likely focus on A) Disease progression in pregnancy B) Natural history of uninfected, HIV-exposed, anti retro-viral exposed infants and C) Impact of HAART on infected adults/children. P2CZ has funded a collaboration with the WITS (0534) to perform Pulmonary fuvetion testing on uninfected, HIV-exposed infants. This study will continue for approximately one year.